Door operator means

ABSTRACT

A power driven operator for a closure or the like where a driven element is moved in a reciprocating manner between fully opened and fully closed limit positions. The power driven operator is interconnected to the driven element to provide back and forth movement without lost motion even during any momentary tendency of the driven element to overrun the drive.

United States Patent MacFarland [54] DOOR OPERATOR MEANS [72] Inventor: Charles H. MacFarland,

River, Ohio 73] Assignee: The Scott &Fetzer Company [22] Filed: June 29, 1970 Rocky 211 App]. No.: 50,845

[52] US. Cl. ..74/89.2l, 49/360, 160/188 [51 Int. Cl ..Fl6h 27/02 [58] Field of Search ...74/89.21, 37; 49/360; 160/188 [56] References Cited UNITED STATES PATENTS 3/ 1965 Wilson ..49/360 1/1956 Franko ..160/188 [15] 3,683,710 [4 1 Aug. 15, 1972 McKee et al., ..74/89.2l Rehwald ..74/37 Primary Examiner-William F. ODea Assistant Examiner-Wesley S. Ratliff, Jr. Aztorney-McNenny, Farrington, Pearne and Gordon [57] ABSTRACT A power driven operator for a closure or the like where a driven element is moved in a reciprocating manner between fully opened and fully closed limit positions. The power driven operator is interconnected to the driven element to provide back and forth movement without lost motion even during any momentary tendency of the driven element to overrun the drive.

11 Claims, 4 Drawing Figures Patented Aug. 15, 1972 2 Sheets-Sheet 2 l I +52 hwy 4 I 60 r- La IT' v DOOR OPERATOR MEANS FIELD OF THE INVENTION This invention relates to power driven operators for a garage door or the like where a driven element may momentarily tend to overrun the drive while it is being driven between fully opened and fully closed positions and, more particularly, to a novel and improved power driven operator which forms a positive drive connection between the drive and the driven element providing reciprocating movement thereof without lost motion.

Although the present invention is useful in such power driven devices generally and should not be otherwise limited, it will be described hereinafter with particular reference to closures such as garage or factory doors.

PRIOR ART The type of power driven operators for garage doors with which this invention is concerned provides reciprocatory movement of the door between fully opened and fully closed limit positions. In such power driven operators, the door is generally guided along a trackway in a first direction to one of the limit positions and in an opposite direction to the other limit position. Typically, the door is retained in an overhead position in the trackway above and rearward of the doorway opening when it is in the fully opened limit position.

The reciprocatory movement of the door is, of course, obtainable by use of a reversible electric motor. In such an installation, the direction of travel of the door is changed by reversing the direction of rotation of the motor. However, it is desirable to employ a nonreversible electric motor, since reversible motors are relatively expensive in comparison and generally require additional installation wiring. Consequently, it is economically preferable to use a non-reversible electric motor in such power driven operators.

When a non-reversible electric motor is employed, the reciprocatory movement of the door is obtained by appropriate mechanical linkages between the drive and the door. The prior art discloses a number of lost motion connections which are utilized to reverse the direction of movement of the driven element or door. Such lost motion connections are generally employed with an endless drive chain which extends about a pair of spaced sprockets, one of which is driven by the electric motor. Reference may be had to US. Pat. No.

2,520,855 for an example of a slotted link lost motion connection employed with an endless drive chain.

The type of lost motion provided in the aforementioned US. Pat. No. 2,520,855 is intended to provide a desired dwell when the door is fully opened or fully closed. However, during movement of the door, the linkage connection is characterized by an undesirable yieldable. or partially unrestrained interconnection between the drive and the driven element which permits uncontrolled movement of the driven elementand a tendency of the door to overrun its drive and/or the drive to overrun the driven element. Consequently, undesirable lost motion during door movement is to be distinguished from a desirable dwell period which exists in the operating cycle at the end of the back and forth movement of the driven element or door.

In such a lost motion connection the drive is not positively driving or restraining the driven element during the period of lost motion during door movement. Therefore, any tendency of the driven element or door to overrun the drive or the drive to overrun the driven element is not positively restrained. As the door is moved along the vertical section of the side tracks toward a closed position, it may overrun the drive and contact the abutting closure surface or base of the doorway opening with substantial force, or may place a sudden load on the motor. Such a jarring impact is, of course, undesirable, since physical and mechanical damage may result with respect to the door as well as the power operator device. In addition, if an obstruction is within the doorway, it also may be contacted by the door with a jarring force.

The prior art also discloses a number of power driven operators for garage doors which employ a single activating signal to turn on the electric motor and to operate latching relays to keep the motor running until the door reaches a fully opened or closed limit position. As the door approaches one of the limit positions, the motor is shut off by a limit switch. For example, the door or drive chain may be provided with a cam surface adapted to operate the limit switch. Although such power driven operators are rather convenient, the additional electrical wiring, including the latching relays, significantly increases their cost.

Such power driven operators are generally provided 1 with an override clutch to disengage the drive if an obstruction prevents the door from traveling a sufficient distance to open the limit switch, since the electric motor will continue to run and drive the door until the limit switch is opened. The override clutch is necessary to prevent the motor from stalling and burning out if the obstruction is not noticed and to prevent the obstruction from being subjected to the driving force of the electric motor as transferred through the door. Consequently, the cost of such power driven operators is also increased by the necessity of an override clutch. In a power driven operator provided with a single actuating switch and a limit switch, a number of safety problems exist. The safety problems are related to the tendency of a person to rely on the limit switch to shut the electric motor off and therefore leave the power operator unattended once the motor has been initially actuated and the doorway opening examined for obstructions. For example, although the doorway is initially found clear of such obstructions, a young child or a careless adult may subsequently come within the path of a closing door. The impact of theclosing door could result in serious physical injury to such a person. Similarly, obstructions could be subsequently placed within the path of the closing door by a person unaware of the fact that the door is being closed. For example, an automobile, a childs toys, gardening tools, or the like could be subsequently positioned within the doorway and subjected to the full impact of the closing door.

In addition, the override clutch itself may cause additional problems when a small obstruction is present in the doorway opening. For exarnple, the handle of a shovel or rake may prevent the door from reaching a fully closed position and opening the limit switch. In this instance, the door would appear to be closed and would not arouse suspicion, although, in fact, the override clutch is engaged and the electric motor continues to operate. Consequently, the electric motor would be subjected to extended periods of operation. This is especially apt to occur in this type of power driven operator, since a person merely provides an actuating signal and expects the limit switch to be opened so as to shut off the electric motor when the door reaches a fully closed position.

SUMMARY OF INVENTION The present invention provides a power driven operator for a closure such as a garage door or like power drive wherein the driven element may momentarily tend to overrun the drive. The door is driven in a reciprocatory manner along a predetermined path to fully opened and closed limit positions. The power driven operator includes a traveler or rigid car which is connected to the door and travels back and forth along a trackway with a dwell at each end of such back and forth movement. The traveler or rigid car is driven back and forth by an endless drive chain and forms a positive drive connection with the drive chain to provide movement of the door without lost motion even during any momentary tendency of the door to overrun the drive.

In the illustrated embodiment of the present invention, the power driven operator is employed with an overhead garage door and is mounted on a frame secured to the ceiling of the garage. The traveler or rigid car moves back and forth along a trackway which is also secured to the ceiling of the garage. The traveler forms an endless drive groove adapted to receive a drive pin projecting from the drive chain. The drive groove is designed to form a positive drive connection with the drive pin at predetermined spaced locations along the drive groove to provide back and forth movement, and travel within the groove during the dwell periods at the end of such movement while the traveler and door remain in a stationary position.

When the drive pin is engaged in a positive drive connection with the traveler, any tendency of the door to overrun the drive is restrained and substantially eliminated. Therefore, the door is smoothly driven to a fully closed limit position without impacting the door against the abutting closure surface or base of the door opening and/or without placing a sudden load on the motor. In this manner, the door and the power driven operator are protected from physical and mechanical damage which otherwise results when the door overruns the drive and impacts against the base of the door opening.

Since the reciprocatory movement of the door is provided by the coaction of the traveler and the drive chain, a non-reversing electric motor is employed in the illustrated embodiment. In addition, a continuous signal switch is used to turn on the electric motor and maintain its operation while the door is being opened or closed. Consequently, the power driven operator of the present invention is relatively inexpensive since a non-reversing electric motor is employed and latching relays are not required to keep the motor running.

Since a continuous signal switch is used to operate the motor, the switch must be manually maintained in a closed position while the door is being opened or closed. Consequently, the switch may be mounted or utilized to provide the person operating the door with a clear view of the door opening so as to substantially eliminate the tendency to close the door on unnoticed obstructions within the door opening. Thus, many of the safety problems described above with reference to prior art devices are eliminated. For example, the tendency for a person to initially check the doorway for obstructions, activate the electric motor to close the door, and then leave the power operator unattended so as to permit the risk of subsequent obstructions, such as a young child at play, to obstruct the doorway is eliminated.

The use of a continuous signal switch also eliminates the need and expense of an override clutch. In-addition, the possibility of the doors engaging a small obstruction, such as the handle of a shovel or rake, so as to appear to have fully closed and opened the limit switch, although in fact the override clutch is engaged and the electric motor is still operating, is eliminated.

Thus, the power driven operator of the present invention is designed to be relatively inexpensive to purchase and install while providing a durable construction which is not adversely affected by the damaging efiects of the driven element or door overruning the drive and forcefully impacting against the abutting closure surface of the doorway. In addition, the power driven operator of the present invention eliminates many of the safety problems which exist in the prior art devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a power driven operator according to the present invention, mounted for movement of an overhead garage door, with parts broken away for clarity;

FIG. 2 is a perspective view on an enlarged scale of the traveler and portions of the trackway and chain drive of the power driven operator shown in FIG. 1;

FIG. 3 is a sectional view of a traveler, trackway, and chain drive with parts omitted for purposes of clarity, the plane of the section being indicated by the line 3-3 in FIG. 2; and

FIG. 4 is a plan view of the traveler and the portion of the trackway when the overhead garage door is in the closed limit position.

DETAILED DESCRIPTION OF THE DRAWINGS Referring to FIG. 1, there is shown an overhead garage door 10 which is formed of hinge-connected sections 12. The door 10 is provided with rollers 14 which are retained in a pair of side tracks 16 (only one of which is shown). Each of the side tracks 16 has a horizontal portion which is essentially parallel to the ceiling of the garage and extends to a curved portion adjacent the doorway opening. Each of the curved portions extends to vertical portions which are located on opposite sides of the doorway opening. The door is moved along the side tracks in a reciprocatory manner between fully opened and fully closed limit positions, the door 10 being illustrated in the fully opened limit position.

Above the horizontal portion of the side track 16 a power driven operator 18 is secured to the ceiling of the garage. The power driven operator includes a nonreversible electric motor which drives an endless drive chain -22 (FIG. 2) about a pair of spaced sprockets 24 and 26. To that end, the electric motor 20 is connected to the sprocket 24 through a speed reduction mechanism indicated schematically at 28. The endless drive chain 22 has two parallel reaches connected by arcuate ends which mesh with the sprockets. Thus, the sprockets define an endless path about which the chain is driven and provide support for the chain.

Intermediate the sprockets 24 and 26, the parallel reaches of the drive chain 22 are positioned within a trackway 30 formed of identical trackway members 32 and 34. As shown in FIG. 1, the sprocket 24 is positioned adjacent the proximal end 36 of the trackway 30 and the sprocket 26 is positioned adjacent the distal end 38 of the trackway. The trackway 30 is secured to the ceiling of the garage by means of fasteners 40, which extend through bores 42 in the trackway members. The fasteners 40 are connected to supports 44 which extend from a cross beam 46, which forms part of the ceiling structure of the garage.

As best shown in FIGS. 2 and 3, the trackway members 32 and 34 cooperate to define a generally U- shaped channel and are laterally spaced to form a guideway opening 48 therebetween. Within the channel formed by the trackway members, a traveler or rigid car 50 is positioned. The traveler 50 has an inverted U-shape having legs 52 and S4 projecting from a connecting member 56. The traveler 50 is designed for sliding reciprocatory movement within the channel formed by the trackway 30.

The movement of the traveler is provided by a drive pin 58, which is connected to the drive chain 22. The drive pin 58 engages the traveler 50 within an endless drive groove 60 formed in the connecting member 56 of the traveler. As set forth below in detail, the drive pin 58 forms a positive drive connection with the traveler to provide reciprocatory movement thereof along the trackway 30 without lost motion. In addition, adjacent the proximal end 36 and the distal end 38 of the trackway 30 the power driven operator is designed to provide a dwell period during which the drive pin 58 34. The shaft 62 is externally threaded adjacent the exposed end thereof and is securely connected to the traveler by means of a nut 66 and spacers 68 and 70. The opposite end of the shaft 62 is connected to a yoke 72 which is pivotally connected to a drive bar 74 by a bolt 76 and a nut 78. The opposite end of the drive bar 74 is connected to the door 10 to provide movement thereof.

The endless drive groove 60 is formed in the connecting member56 of the traveler 50 by an elongated opening having arcuate ends and a central island portion 80. The central island portion 80 has similar but smaller dimensions than those of the elongated opening, and it is centrally mounted therein. Accordingly, the drive groove 60 has elongated parallel side portions which are connected by arcuate end portions. The side portions are spaced apart a distance substantially equal to the distance between the parallel reaches of the drive chain 22 and each of the associated side portions and parallel reaches are substantially vertically aligned.

The connecting member 56 forms an outer peripheral wall 82 of the drive groove 60 and the central island portion forms an inner peripheral wall 84 thereof. The central island portion is held in position by means of the shaft 62 and a bridging support 86, which is welded to the connecting member 56.

The peripheral walls 82 and 84 of the drive groove 60 are spaced apart a sufiicient distance to receive the drive pin 58. The drive pin extends through the drive groove 60 and projects a short distance beyond the connecting member 56 and the central island portion 80. The bridging support 86 has a pair of arched sections 86a and 86b adjacent the drive groove 60 to provide clearance for the projecting extremities of the drive pin 58. j

The traveler 50 includes a pair of latches 88 and 90 which are pivotally secured to the central island portion 80 by pins 92 and 94, respectively. The latch 88 is biased against a stop pin 96 which extends from the connecting member 56 by a spring 98. Similarly, the

latch 90 is biased against a stop pin 100 by a spring 102.

The latches extend across the drive groove 60 and are designed to engage the projecting extremities of the drive pin 58 at predetermined spaced locations as it travels within the drive groove 60. Since the latches are arranged to rotate or open in one direction only with respect to the traveler, the drive pin 58 is permitted to travel within the drive groove in only one direction.

OPERATION Referring to FIG. 2, the power driven operator 18 is shown in a positive drive connection wherein the door l0is being moved to a fully closed limit position. As the traveler 50 moves along the trackway 30 towards the distal end 38 thereof, the drive pin v58 works against the outer peripheral wall 82 of the connecting member 56, adjacent a predetermined location within the drive groove 60.

The positive drive connection is formed adjacent an arcuate end of the drive groove 60. In order to augment the mechanical engagement of the drive pin and the traveler, the arcuate end portion of the drive groove extends in a direction such that the greatest resultant force applied by the drive pin to the traveler is in the direction of movement of the traveler. The latch 88 also tends to retain the drive pin in the positive drive connection and inhibit any tendency of the drive pin to move laterally or deviate from the direction of movement of the traveler.

As the traveler moves along the trackway 30, the door 10 is moved along the horizontal portion of the side tracks 16 and down the vertical portion thereof by the drive bar 74 which is pivotally connected to the shaft 62 of the traveler. Themovement of the shaft 62, which is rigidly connected to the traveler, is further aligned by means of the guideway opening 48 in which the shaft travels.

' As the door travels down the vertical portion of the side tracks 16, any tendency of the door to overrun the drive is substantially eliminated by the positive drive connection between the drive pin 58 and the traveler 50. For example, if the door tends: to overrun and advance the traveler ahead of the drive pin 58, the door and the traveler are restrained by the drive pin working against the latch 88. The latch 88 prevents counterclockwise movement of the drive pin 58 in the drive groove 60 and advancement of the traveler ahead of the drive pin by means of the stop pin 96 against which the latch abuts.

The door 10 reaches the fully closed limit position when the drive pin 58 reaches the line A-A shown in FIG. 4. The line A-A passes through the axis of the sprocket 26 and is substantially perpendicular to the direction of movement of the approaching drive pin. At this point, the drive pin 58 has not begun to travel about the arcuate path defined by the sprocket 26, and the door has been fully closed without any lost motion. The door is smoothly moved to the closed position without impacting against the base of the doorway opening, since any tendency for the door to overrun the drive is eliminated and the latch 88 effectively locks the drive pin in the driving position.

As shown in FIG. 4, the traveler 50 and the drive pin 58 begin a dwell period at this time. During the dwell period, the door and traveler remain in a substantially stationary position as the drive pin travels about the arcuate periphery of the sprocket. A small amount of movement will occur as the drive pin moves from the phantom position shown adjacent the line A-A to the dead center position. This movement occurs since the drive groove 60 is not provided with a semicircular configuration adjacent its arcuate ends.

Although the drive groove 60 could be provided with such a configuration, it is preferably not, since difficulties may be encountered in retaining the drive pin in a positive drive connection adjacent a circular outer peripheral wall. In addition, any slight forward movement of the door which is caused by the non-circular configuration of the drive groove is essentially taken up by the door seals, the linkage between the traveler and the door, and the hinged door sections 12.

As the drive pin 58 moves from the dead center position around the sprocket 26 in the clockwise direction, a small amount of movement of the door in an opposite direction will occur. This movement will similarly be taken up in the door seals, the linkage between the traveler and the door, and door sections so that the door will not be opened. The drive pin will continue to travel along the drive groove 60 without movement of the traveler or the door towards the latch 90. This dwell period is provided to allow a person operating the door sufficient time to shut down the electric motor 20. Thus, a continuous signal switch (not shown) is used to operate the electric motor and an adequate dwell period during which the switch may be opened is provided. Of course, the power driven operator 18 may be provided with a single activating switch, latching relays, and a limit switch, since a suitable dwell period exists after the door has been moved to a fully closed limit position.

After the door has been closed, the drive pin 58 may be positioned along the drive groove 60 in any of the dwell locations described above. Consequently, when the door is opened, the drive pin 58 will travel within the drive groove 60 until it engages the latch 90, causing it to rotate or open so as to receive the drive pin. The spring 102 then closes the latch, biasing it against the stop pin 100, to provide a second positive drive connection adjacent the arcuate end of the drive groove substantially identical to that previously described with respect to the latch 88. As the drive chain 22 continues to travel about the sprockets 24 and 26, the drive pin 58 moves the traveler and the door towards the proximal end 36 of the trackway 30. The door is moved to a fully opened limit position in a smooth and uniform manner, since the drive pin and the traveler are engaged in a positive drive connection identical to that described above. Thus, the door is moved to the fully opened limit position without lost motion. Afier the door reaches the fully opened limit position, the drive pin 58 disengages from the positive drive connection and begins to travel around the sprocket 24 and a second dwell period begins. This dwell period is similarly provided to allow the person operating the power driven operator adequate time to open the continuous signal switch and shut off the electric motor 20.

As described above, the traveler is interconnected to the drive chain so as to move the door through the fully opened and fully closed limit positions without lost motion. During movement of the door, the drive pin forms a positive drive connection within the drive groove at predetermined spaced locations and any tendency of the door to overrun the drive is restrained and substantially eliminated. Consequently, the door is smoothly driven to a fully closed limit position without impacting the door against the abutting closure surface or baseof the doorway opening. Thus, the door and the power driven operator are protected from the jarring impact which otherwise results when the door overruns the drive as the door travels down the vertical section of the side trackways to a fully closed limit position.

Since the power driven operator employs a continuous signal switch, it is impossible for the person operating the door to actuate the closing of the door and then leave it unattended. Thus, the safety problems existing in prior art devices involving obstructions which subsequently enter within the path of the closing unattended door are eliminated. In addition, the use of a continuous signal switch eliminates the need for limit switches, latching relays, and an override clutch. Con sequently, the power driven operator of the present invention is relatively inexpensive and provides a durable construction.

The invention is not restricted to the slavish imitation of each and every detail set forth above. Obviously, devices may be provided which change, eliminate, or add certain specific details without departing from the scope of the invention.

What is claimed is:

1. In a power driven garage door operator or like power driven operator where a driven element may momentarily tend to overrun the drive while it is driven between fully opened and fully closed positions, a driven element, endless flexible drive means having two long parallel reaches, track means extending along the reaches, traveler means linked to the driven element and guided by the track means, the traveler means being interconnected with the drive means for back and forth driven movement of the traveler means along the track means, said traveler means including means providing a dwell for said driven element at each end of such back and forth movement and including locking means to prevent lost motion during said movement of said driven element, said flexible drive means including drive pin means positioned in and adapted to travel along an endless drive groove means provided by said traveler means, said drive pin means forming a positive drive connection with said traveler means at predetermined spaced locations along said drive groove means to provide back and forth movement of said traveler means, said drive pin means being adapted to move along said drive groove means during said dwell at each end of such back and forth movement while said traveler means remains in a substantially stationary position.

2. A device as set forth in claim 1, wherein said locking means includes latch means to retain said drive pin means in said positive drive connection and to permit movement of said drive pin along said drive groove means in only one direction.

3. A device as set forth in claim 2, wherein said drive groove means adjacent said predetermined spaced locations engages said drive pin means so that the greatest resultant force is in the direction of movement of said traveler.

4. A device as set forth in claim 2, wherein said traveler means includes a rigid car designed to travel along said track means and said endless drive groove means comprises an endless groove defined by said car having spaced walls adapted to received said drive pin means therebetween, and said drive pin means includes a drive pin projecting from said endless flexible drive means.

5. A device as set forth in claim 4, wherein said latch means includes a pair of latches pivotally connected to said rigid car, each one of said latches being pivotally connected to said rigid car adjacent each of said predetermined spaced locations.

6. A device as set forth in claim 5, wherein said rigid car has a substantially inverted U-shaped configuration having projecting legs adapted for sliding movement in a channel defined by said track means.

7. A device as set forth in claim 6, wherein said track means includes a pair of U-shaped tracks cooperating to define said channel, said tracks being laterally spaced to define an elongated guideway opening therebetween.

8. A device as set forth in claim 7, wherein said endless drive groove is defined by an elongated opening having arcuate ends in a connecting member portion of said rigid car extending between said projecting legs and by a central island-portion mounted within said opening, said island portion having similar but smaller dimensions Gian said elongated opening.

9. A device as set forth in claim 8, wherein said rigid car includes a shaft pivotally connected to said driven element, said shaft extending through said elongated guideway opening and adapted for sliding movement therein.

10. A device as set forth in claim 9, wherein said endless flexible drive means includes an endless drive chain having parallel reaches and arcuate ends, and sprockets engaging and supporting said chain adjacent said ends.

11. A device a set forth in claim 10, wherein said sprockets. 

1. In a power driven garage door operator or like power driven operator where a driven element may momentarily tend to overrun the drive while it is driven between fully opened and fully closed positions, a driven element, endless flexible drive means having two long parallel reaches, track means extending along the reaches, traveler means linked to the driven element and guided by the track means, the traveler means being interconnected with the drive means for back and forth driven movement of the traveler means along the track means, said traveler means including means providing a dwell for said driven element at each end of such back and forth movement and including locking means to prevent lost motion during said movement of said driven element, said flexible drive means including drive pin means positioned in and adapted to travel along an endless drive groove means provided by said traveler means, said drive pin means forming a positive drive connection with said traveler means at predetermined spaced locations along said drive groove means to provide back and forth movement of said traveler means, said drive pin means being adapted to move along said drive groove means during said dwell aT each end of such back and forth movement while said traveler means remains in a substantially stationary position.
 2. A device as set forth in claim 1, wherein said locking means includes latch means to retain said drive pin means in said positive drive connection and to permit movement of said drive pin along said drive groove means in only one direction.
 3. A device as set forth in claim 2, wherein said drive groove means adjacent said predetermined spaced locations engages said drive pin means so that the greatest resultant force is in the direction of movement of said traveler.
 4. A device as set forth in claim 2, wherein said traveler means includes a rigid car designed to travel along said track means and said endless drive groove means comprises an endless groove defined by said car having spaced walls adapted to received said drive pin means therebetween, and said drive pin means includes a drive pin projecting from said endless flexible drive means.
 5. A device as set forth in claim 4, wherein said latch means includes a pair of latches pivotally connected to said rigid car, each one of said latches being pivotally connected to said rigid car adjacent each of said predetermined spaced locations.
 6. A device as set forth in claim 5, wherein said rigid car has a substantially inverted U-shaped configuration having projecting legs adapted for sliding movement in a channel defined by said track means.
 7. A device as set forth in claim 6, wherein said track means includes a pair of U-shaped tracks cooperating to define said channel, said tracks being laterally spaced to define an elongated guideway opening therebetween.
 8. A device as set forth in claim 7, wherein said endless drive groove is defined by an elongated opening having arcuate ends in a connecting member portion of said rigid car extending between said projecting legs and by a central island portion mounted within said opening, said island portion having similar but smaller dimensions than said elongated opening.
 9. A device as set forth in claim 8, wherein said rigid car includes a shaft pivotally connected to said driven element, said shaft extending through said elongated guideway opening and adapted for sliding movement therein.
 10. A device as set forth in claim 9, wherein said endless flexible drive means includes an endless drive chain having parallel reaches and arcuate ends, and sprockets engaging and supporting said chain adjacent said ends.
 11. A device a set forth in claim 10, wherein said endless flexible drive means includes a non-reversible electric motor operatively connected to one of said sprockets. 